Helicopter Vibration Reduction Throughout the Entire Flight Envelope Using Surrogate Based Optimization

The effectiveness of surrogate based optimization of helicopter rotor blades for vibration reduction at both low speed and high speed forward flight is studied. The Efficient Global Optimization (EGO) algorithm is used to conduct a global search of the design space. Vibration levels in the low speed regime are caused primarily by blade-vortex interaction and vibrations at high advance ratios are caused by dynamic stall. Although the source of high vibrations is different for both flight conditions, the results show that the EGO algorithm is effective in finding reduced vibration designs at both flight conditions. Furthermore, the results indicate that it is possible to design a blade with reduced vibration levels at both flight conditions. Clearly, for the best possible design judicious trade-offs are required.